You want to know if the Messaging Gateway supports the SMTP service extension SMTPUTF8, which is an extension that supports internationalized email addresses or message header information.
As of version 10.8.1, the SMTPUTF8 extension is not currently supported by the Messaging Gateway. It is slated to be introduced in a newer version of the Messaging Gateway. Subscribe to this article to keep updated.
This extension is defined in RFC 6531: https://datatracker.ietf.org/doc/html/rfc6531